Thermoplastic liquid-crystalline polymer (which is called as liquid-crystalline polymer or LCP hereinafter) has good properties including heat resistance, mechanical properties such as rigidity, chemical resistance and dimensional accuracy. Due to those properties, LCPs are used not only for manufacturing molded articles but also for a variety of products including fibers and films. Particularly, personal computers and mobile phones employ highly integrated devices and the art wishes to use downsized, thinner and smaller parts for them. In the information and telecommunication fields, very thin parts are sometimes required. Based on the excellent properties of the LCPs, consumption of the LCPs has been increasing.
Recently, indoor equipments of air-conditioning machines are required to be downsized, and the art wishes to use downsized, thinner and smaller parts for indoor equipments such as a cross flow fan. Conventionally, plastic materials such as acrylic styrene resin have been used for manufacturing cross flow fans. However the acrylic styrene resin is not suitable for parts of 0.8 mm or less of the thickness. It is difficult to completely fill a die for such a thin part using said resin by injection molding. In addition, the cross flow fan made of the acrylic styrene resin tends to be deformed due to warpage of parts. Moreover, high-speed rotation of the cross flow fan is required to compensate the decrease in blast volume due to downsizing of the indoor equipment. For manufacturing downsized cross flow fans, the art desires a material with high modulus of elongation and high mechanical strength which is resistant to high-speed rotation. LCPs are thought to hold promise as materials which may solve the problem due to downsizing of parts and may show high mechanical strength.
Among the various liquid-crystalline polymers, a liquid-crystalline polyester amide comprising a certain amount of 6-oxy-2-naphthoyl repeating unit in its molecular chain shows high modulus of elongation (Japanese Patent Application Laid Open No. Sho. 57-172921 equivalent to U.S. Pat. No. 4,330,457 and Japanese Patent Application Laid Open No. Sho. 61-51032, the contents of those references are herein incorporated by the reference). However, the liquid-crystalline polymers with high modulus of elongation may generally exhibit high melt viscosity and low flowability and therefore, are not suitable for manufacturing molded articles having thin parts.
In addition, LCPs have higher melting point and require higher processing temperature than resin materials such as acrylic styrene resin conventionally used for producing cross flow fans. Accordingly, if parts made of such LCPs were subjected to secondary processing such as welding, a jointed article with sufficient joint strength could hardly be obtained.
Accordingly, LCPs which exhibit appropriate valance between molding flowability and modulus of elongation as well as excellent molding processability at low temperatures are desired. Parts made of such LCPs may be easily processed by a secondary processing operation such as welding.
In order to improve the flowability of LCPs with high modulus of elongation, for example, a polymer blend comprising a liquid-crystalline polyester amide such as those disclosed in Japanese Patent Application Laid Open No. Sho. 57-172921 equivalent to U.S. Pat. No. 4,330,457 and Japanese Patent Application Laid Open No. Sho. 61-51032 and a wholly aromatic liquid-crystalline polyester (see Japanese Patent Application Laid Open No. Sho. 61-120851 equivalent to U.S. Pat. No. 4,567,227) has been proposed. However said polymer blend needs to be processed at temperatures equal to or higher than 250° C. and exhibits poor molding processability at low temperatures. The molding flowability of the polymer blend is also not satisfiable. In addition, due to its high processing temperature, the polymer blend has only poor weldability and is not suitable for manufacturing downsized cross flow fans.